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United States Patent | 5,642,045 |
Keefe ,   et al. | June 24, 1997 |
An improved magnetic field gradiometer having major and minor correction circuits is disclosed. The major correction circuits cancel the main components of an applied magnetic field, such as the earth's uniform field, and the minor correction circuits correct for smaller, but still significant effects, such as assembly imperfections and unavoidable cross-talk between the elements of the gradiometer. Also disclosed is a method for processing the gradient data from the gradiometer to enable the positions of magnetic objects to be located in space.
Inventors: | Keefe; George Andrew (Montrose, NY); Koch; Roger Hilsen (Amawalk, NY) |
Assignee: | International Business Machines Corporation (Armonk, NY) |
Appl. No.: | 516846 |
Filed: | August 18, 1995 |
Current U.S. Class: | 324/244; 324/225; 324/247; 324/253; 324/345; 702/104 |
Intern'l Class: | G01R 033/022; G01R 033/025; G01R 033/04; G01V 003/08 |
Field of Search: | 324/225,244,245,247,248,249,251-255,258,260,345,346 33/355 R-357,363 R 340/870.33 364/571.01,571.02 |
3398360 | Aug., 1968 | Behr et al. | 324/254. |
4327498 | May., 1982 | Setter et al. | 324/225. |
4475078 | Oct., 1984 | Itani | 324/254. |
5113136 | May., 1992 | Hayashi et al. | 324/248. |
5122744 | Jun., 1992 | Koch | 324/248. |
5187436 | Feb., 1993 | Mallick | 324/225. |
W.M. Wynn et al, IEEE Transactions on Magnetics, vol. MAG-11, No. 2, Mar. 1975 pp. 701-707, entitled "Advanced Superconducting Gradiometer/Magnetometer Arrays and a Novel Signal Processing Technique". |